Systems, methods, and apparatus for production coatings of low-emissivity glass

ABSTRACT

Disclosed herein are systems, methods, and apparatus for forming a low emissivity panel. In various embodiments, a partially fabricated panel may be provided. The partially fabricated panel may include a substrate, a reflective layer formed over the substrate, and a top dielectric layer formed over the reflective layer such that the reflective layer is formed between the substrate and the top dielectric layer. The top dielectric layer may include tin having an oxidation state of +4. An interface layer may be formed over the top dielectric layer. A top diffusion layer may be formed over the interface layer. The top diffusion layer may be formed in a nitrogen plasma environment. The interface layer may substantially prevent nitrogen from the nitrogen plasma environment from reaching the top dielectric layer and changing the oxidation state of tin included in the top dielectric layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application 61/778,758, filed on 2013 Mar. 13, whichis incorporated herein by reference in its entirety for all purposes.

TECHNICAL FIELD

The present disclosure relates generally to films providing hightransmittance and low emissivity, and more particularly to such filmsdeposited on transparent substrates.

BACKGROUND

Sunlight control materials, such as treated glass sheets, are commonlyused for building glass windows and vehicle windows. Such materialstypically offer high visible transmission and low emissivity therebyallowing more sunlight to pass through the glass window while blockinfrared (IR) radiation to reduce undesirable interior heating. In lowemissivity (low-E) materials, IR radiation is mostly reflected withminimum absorption and emission, thus reducing the heat transferring toand from the low emissivity surface. Low-E panels are often formed bydepositing a reflective layer (e.g., silver) onto a substrate, such asglass. The overall quality of the reflective layer is important forachieving the desired performance. In order to provide adhesion, as wellas protection, several other layers are typically formed both under andover the reflective layer. These layers typically include dielectriclayers, such as silicon nitride, tin oxide, and zinc oxide, whichprovide protect the stack from both the substrate and the environment.The dielectric layer may also act as optical fillers and function asanti-reflective coating layers to improve the optical characteristics ofthe panel.

A typical approach to reduce emissivity involves increasing thethickness of the reflective layer (e.g., the silver layer). However, asthe thickness of the reflective layer increases, the visible lighttransmission of this layer is also reduced. Furthermore, the highthickness slows manufacturing throughput and increases costs. It may bedesirable to keep the reflective layer as thin as possible, while stillproviding emissivity suitable for low-e applications.

SUMMARY

Disclosed herein are systems, methods, and apparatus for forminglow-emissivity (low-E) panels. In some embodiments, the methods mayinvolve providing a partially fabricated panel. The partially fabricatedpanel may include a substrate, a reflective layer formed over thesubstrate, and a top dielectric layer formed over the reflective layersuch that the reflective layer is formed between the substrate and thetop dielectric layer. The top dielectric layer may include tin having anoxidation state of +4. The methods may proceed with forming an interfacelayer over the top dielectric layer and forming a top diffusion layerover the interface layer. The top diffusion layer is formed in anitrogen plasma environment. In some embodiments, the interface layerhas a band gap of at least 3.0 eV. In some embodiments, a material ofthe interface layer may be at least about 25% amorphous. The interfacelayer substantially prevents nitrogen from the nitrogen plasmaenvironment from reaching the top dielectric layer.

The interface layer may directly interface the top diffusion layer andthe top dielectric layer. In some embodiments, tin of the top dielectriclayer is formed from one of tin oxide, zinc tin oxide, aluminum tinoxide, magnesium tin oxide, bismuth tin oxide, or niobium tin oxide. Amaterial of the interface layer may be at least about 50% amorphous.Moreover, a material of the interface layer may be less than 5%crystalline by volume, as determined by X-ray diffraction. The interfacelayer may include one of zinc oxide, titanium oxide, or tantalum oxide.The interface layer may have a thickness of between about 2 nanometersand 8 nanometers. The top diffusion layer may include silicon nitride.The top diffusion layer may be formed using sputtering of a silicontarget in a nitrogen plasma environment. In some embodiments, thepartially fabricated panel also includes a barrier layer formed betweenthe reflective layer and the dielectric layer. The barrier layer mayinclude nickel, titanium, and niobium. In some embodiments, thepartially fabricated panel further includes a bottom diffusion layerdeposited or formed between the substrate and the reflective layer, abottom dielectric layer deposited or formed between the bottom diffusionlayer and the substrate, and a seed layer formed between the bottomdielectric layer and the reflective layer.

The methods may involve, after forming the top diffusion layer, heattreating the partially fabricated panel. During this heat treatment, thepartially fabricated panel may include the interface layer and the topdiffusion layer. A change in a substrate-side reflectance of thispartially fabricated panel may be less than 3% after heat treating.

In some embodiments, the interface layer may be formed using adeposition technique, such as reactive sputtering. The top diffusionlayer may include silicon nitride. The interface layer includes zincoxide, while the top dielectric layer includes zinc tin oxide.Substantially all tin in the dielectric layer may have the oxidationstate of +4.

Also disclosed herein are methods of forming a low emissivity panel. Insome embodiments, the methods involve providing a partially fabricatedpanel. The partially fabricated panel includes a glass substrate, areflective layer formed over the glass substrate, and a top dielectriclayer formed over the reflective layer such that the reflective layer isformed between the substrate and the dielectric layer. The topdielectric layer includes zinc tin oxide. The methods proceed withforming an interface layer over the top dielectric layer. The interfacelayer includes zinc oxide and has a thickness of between about 2 nm and8 nm. Moreover, the interface layer may have a band gap of at least 3.0eV. In some embodiments, a material of the interface layer is at leastabout 50% amorphous. The methods proceed with forming a top diffusionlayer over the interface layer. The top diffusion layer includes siliconnitride and may be formed using reactive sputtering in a nitrogen plasmaenvironment. In some embodiments, the interface layer substantiallyprevents nitrogen from the nitrogen plasma environment from reaching thetop dielectric layer and changing an oxidation state of tin in the topdielectric layer.

Also disclosed herein are low emissivity panels. In some embodiments,the panels may include a substrate, a reflective layer formed over thesubstrate, a top dielectric layer formed over the reflective layer suchthat the reflective layer is formed between the substrate and the topdielectric layer. The top dielectric layer also includes tin having anoxidation state of +4. The panels also include an interface layer formedover the top dielectric layer such that the top dielectric layer isformed between the reflective layer and the interface layer. Theinterface layer may include one of zinc oxide, titanium oxide, ortantalum oxide. Moreover, the interface layer may have a band gap of atleast 3.0 eV. In some embodiments, a material of the interface layer isat least about 50% amorphous. The panels also include a top diffusionlayer formed over the interface layer such that the interface layer isformed between the top dielectric layer and the interface layer. The topdiffusion layer includes silicon nitride.

These and other embodiments are described further below with referenceto the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

To facilitate understanding, the same reference numerals have been used,where possible, to designate common components presented in the figures.The drawings are not to scale and the relative dimensions of variouselements in the drawings are depicted schematically and not necessarilyto scale. Various embodiments can readily be understood by consideringthe following detailed description in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic illustration of an article including a substrateand a stack of layers including one reflective layer formed over thesubstrate, in accordance with some embodiments.

FIG. 2 is a schematic illustration of another article including asubstrate and a stack of layers including two reflective layers formedover the substrate, in accordance with some embodiments.

FIG. 3 is a schematic illustration of yet another article including asubstrate and a stack of layers including three reflective layers formedover the substrate, in accordance with some embodiments.

FIG. 4 is a process flowchart corresponding to a method for forming anarticle including a reflective layer and a barrier layer for protectingmaterials in this reflective layer from oxidation, in accordance withsome embodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the presented concepts. Thepresented concepts may be practiced without some or all of thesespecific details. In other instances, well known process operations havenot been described in detail so as to not unnecessarily obscure thedescribed concepts. While some concepts will be described in conjunctionwith the specific embodiments, it will be understood that theseembodiments are not intended to be limiting.

Introduction

Provided are methods of forming low emissivity panels having topdielectric layers protected by interface layers during subsequentprocessing of the panels. Also provided are panels formed by suchmethods. A low emissivity panel may include a top dielectric layerformed by tin oxide, zinc tin oxide, aluminum tin oxide, magnesium tinoxide, bismuth tin oxide, or niobium tin oxide. Tin of the topdielectric layer may be predominantly in an oxidation state of +4providing suitable optical transmission properties to the top dielectriclayer. However, this oxidation state is unstable, and tin can easilytransition into +2 oxidation state, which reduces transmission of thetop dielectric layer. The top dielectric layer is particularlysusceptible to this change in tin's oxidation state and deterioration ofthe layer's transmission properties when a top diffusion layer is formedover the top dielectric layer. The top diffusion layer is typicallyformed by reactive sputtering of silicon in a nitrogen plasmaenvironment. The activated nitrogen in the nitrogen plasma environmentis very reactive and can easily convert tin from one oxidation intoanother. Specifically, when the top dielectric layer is exposed to thenitrogen plasma environment it may undergo the undesired changesdescribe above.

Conventional methods of fabricating low emissivity panels may use topdielectric layers that do not couple or connect to nitrides well. Thus,conventional methods do not provide good coupling between the topdielectric layer and the top diffusion layer. Moreover, conventionalmethods do not isolate and protect the top dielectric layer from changesin its oxidation state which may occur during deposition of the topdiffusion layer, or during subsequent manufacturing processes, such as aheat treatment that may be used to temper the glass. Furthermore,conventional methods to not provide protection for the top dielectriclayer in a way that is compatible with multiple manufacturing processes.For example, conventional production coatings in low emissivity panelsmay be different for an as-coated (AC) panel than those used for a heattreatment (HT) panel. The use of different production coatings fordifferent processes results in increased costs and increased productiontimes.

In some embodiments disclosed herein, in order to protect the topdielectric layer and maintain its optical transmission properties, aninterface layer is formed over the top dielectric layer before formingany other layers or exposing the top dielectric layer to any damagingenvironments, such as nitrogen plasma. The interface layer may be formedfrom high band gap materials that are highly transmissive and havestrong oxygen bonds. Some examples of such materials include zinc oxide,titanium oxide, and tantalum oxides. The thickness of the interfacelayer may be between about 2 nm and 8 nm or, more specifically, betweenabout 3 nm and 5 nm. A thinner interface layer may not be sufficientlyconformal and/or protective. On the other hand, a thicker interfacelayer may be more susceptible to crystallization, which may beundesirable. In some embodiments, the interface layer is at least about25% amorphous or even at least about 50% amorphous.

The interface layer prevents contact between tin in the top dielectriclayer and nitrogen in the plasma used to form the top diffusion layer.Furthermore, the interface layer prevents oxygen migration from the topdielectric layer. Overall, the interface layer substantially inhibitschanges in the oxidation state of tin in the top dielectric layerresulting in more stable transmissive and color properties of the topdielectric layer. While the effects of the interface layer may be themost prominent during formation of the top diffusion layer, theinterface layer may also protect the top dielectric layer even after thetop diffusion layer is formed. For example, a low emissivity panel maybe subjected to heat treatment or forming additional layers over the topdiffusion layer. Such processes may cause materials to diffuse in or outof the top dielectric layer if the interface layer is not present. Theinterface layer may be used in low emissivity panels that are latersubject to heat treatment as well as in low emissivity panels that areused without subsequent heat treatment.

Examples of Low-Emissivity Coatings

A brief description of low-E coatings is provided for context and betterunderstanding of various features associated with barrier layers andsilver reflective layers. One having ordinary skills in the art wouldunderstand that these barrier and silver reflective layers may be alsoused for other applications, such as light emitting diodes (LED),reflectors, and other like applications. Some characteristics of low-Ecoatings are applicable to these other applications as well. Forpurposes of this disclosure, low-E is a quality of a surface that emitslow levels of radiant thermal energy. Emissivity is the value given tomaterials based on the ratio of heat emitted compared to a blackbody, ona scale of 0 (for a perfect reflector) to 1 (for a back body). Theemissivity of a polished silver surface is 0.02. Reflectivity isinversely related to emissivity. When values of reflectivity andemissivity are added together, their total is equal 1.

FIG. 1 is a schematic illustration of an article 100 including asubstrate 102 and a stack 120 of layers 104-116, in accordance with someembodiments. Specifically, stack 120 includes one reflective layer 110formed over substrate 102 and protected by a barrier layer 112. Otherlayers in stack 120 may include bottom diffusion layer 104, topdiffusion layer 116, bottom dielectric layer 106, top dielectric layer114, and seed layer 108. Each one of these components will now bedescribed in more details. One having ordinary skills in the art wouldunderstand that the stack may include fewer layers or more layers as,for example, described below with reference to FIGS. 2 and 3.

Substrate 102 can be made of any suitable material. Substrate 102 may beopaque, translucent, or transparent to the visible light. For example,for low-E applications, the substrate may be transparent. Specifically,a transparent glass substrate may be used for this and otherapplications. For purposes of this disclosure, the term “transparency”is defined as a substrate characteristic related to a visible lighttransmittance through the substrate. The term “translucent” is definedas a property of passing the visible light through the substrate anddiffusing this energy within the substrate, such that an objectpositioned on one side of the substrate is not visible on the other sideof the substrate. The term “opaque” is defined as a visible lighttransmittance of 0%. Some examples of suitable materials for substrate102 include, but are not limited to, plastic substrates, such as acrylicpolymers (e.g., polyacrylates, polyalkyl methacrylates, includingpolymethyl methacrylates, polyethyl methacrylates, polypropylmethacrylates, and the like), polyurethanes, polycarbonates, polyalkylterephthalates (e.g., polyethylene terephthalate (PET), polypropyleneterephthalates, polybutylene terephthalates, and the like), polysiloxanecontaining polymers, copolymers of any monomers for preparing these, orany mixtures thereof. Substrate 102 may be also made from one or moremetals, such as galvanized steel, stainless steel, and aluminum. Otherexamples of substrate materials include ceramics, glass, and variousmixtures or combinations of any of the above.

Bottom diffusion layer 104 and top diffusion layer 116 may be two layersof stack 120 that protect the entire stack 120 from the environment andimprove chemical and/or mechanical durability of stack 120. Diffusionlayers 104 and 116 may be made from the same or different materials andmay have the same or different thickness. In some embodiments, one orboth diffusion layers 104 and 116 are formed from silicon nitride. Insome embodiments, silicon nitride may be doped with aluminum and/orzirconium. The dopant concentration may be between about 0% to 20% byweight. In some embodiments, silicon nitride may be partially oxidized.Silicon nitride diffusion layers may be silicon-rich, such that theircompositions may be represented by the following expression,Si_(x)N_(y), where the X-to-Y ratio is between about 0.8 and 1.0. Therefraction index of one or both diffusion layers 104 and 116 may bebetween about 2.0 and 2.5 or, more specifically, between about 2.15 to2.25. The thickness of one or both diffusion layers 104 and 116 may bebetween about 50 Angstroms and 300 Angstroms or, more specifically,between about 100 Angstroms and 200 Angstroms.

In addition to protecting stack 120 from the environment, bottomdiffusion layer 104 may help with adhering bottom dielectric layer 106to substrate 102. Without being restricted to any particular theory, itis believed that deposition of dielectric layer 106 and in particularsubsequent heat treatment of this layer results in heat-inducedmechanical stresses at the interfaces of dielectric layer 106. Thesestresses may cause delamination of dielectric layer 106 from otherlayers and coating failure. A particular example is a titanium oxidelayer deposited directly onto the glass substrate. However, when siliconnitride diffusion layer 104 is provided between bottom dielectric layer106 and substrate 102, the adhesion within this three-layer stackremains strong as evidenced by improved durability, especially afterheat treatment.

Typically, each reflective layer provided in a stack is surrounded bytwo dielectric layers, e.g., bottom dielectric layer 106 and topdielectric layer 114 as shown in FIG. 1. Dielectric layers 106 and 114are used to control reflection characteristics of reflective layer 110as well as overall transparency and color of stack 120 and, in someembodiments, of article 100. Dielectric layers 106 and 114 may be madefrom the same or different materials and may have the same or differentthickness. In some embodiments, one or both dielectric layers 106 and114 are formed from TiO₂, ZnO, SnO₂, SiAlN, or ZnSn. In general,dielectric layers 106 and 114 may be formed from various oxides,stannates, nitrides, and/or oxynitrides. In some embodiments, one orboth dielectric layers 106 and 114 may include dopants, such as Al, Ga,In, Mg, Ca, Sr, Sb, Bi, Ti, V, Y, Zr, Nb, Hf, or Ta. Dielectric layers106 and 114 can each include different dielectric materials with similarrefractive indices or different materials with different refractiveindices. The relative thicknesses of the dielectric films can be variedto optimize thermal-management performance, aesthetics, and/ordurability of article 100.

The materials of dielectric layers 106 and 114 may be in amorphousphases, crystalline phases, or a combination of two or more phases. Insome embodiments, when stack 120 includes seed layer 108, bottomdielectric layer 106 may be in an amorphous phase. Alternatively, whenstack 120 does not include seed layer 108, bottom dielectric layer 106may be in a crystalline phase and function as a nucleation template foroverlying layers, e.g., reflective layer 110. In some embodiments, acrystalline phase may be greater than 30% crystalline as determined byX-ray diffraction. The thickness of dielectric layers 106 and 114 may bebetween about 50 Angstroms and 1000 Angstroms or, more specifically,between 100 Angstroms and 300 Angstroms.

In some embodiments, stack 120 includes seed layer 108. Seed layer 108may be formed from ZnO, SnO₂, Sc₂O₃, Y₂O₃, TiO₂, ZrO₂, HfO₂, V₂O₅,Nb₂O₅, Ta₂O₅, CrO₃, WO₃, MoO₃, various combinations thereof, or othermetal oxides. The material of seed layer 108 may be in a crystallinephase. Seed layer 108 may function as a nucleation template foroverlying layers, e.g., reflective layer 110. In some embodiments, thethickness of seed layer 108 is between about 50 Angstroms and 200Angstroms, such as about 100 Angstroms.

Stack 120 includes reflective layer 110, which is formed from silver.The thickness of this layer may be between about 50 Angstroms and 200Angstroms or, more specifically, between about 100 Angstroms and 150Angstroms.

As noted above, stack 120 also includes barrier layer 112 to protectreflective layer 110 from oxidation and other damage. Barrier layer 112may be formed from a quaternary alloy that includes nickel, chromium,titanium, and aluminum. The concentration of each metal in this alloy isselected to provide adequate transparency and oxygen diffusion blockingproperties. In some embodiments, a combined concentration of nickel andchromium in the barrier layer is between about 20% by weight and 50% byweight or, more specifically, between about 30% by weight and 40% byweight. A weight ratio of nickel to chromium in the alloy may be betweenabout 3 and 5 or, more specifically, about 4. A weight ratio of titaniumto aluminum is between about 0.5 and 2, or more, specifically about 1.In some embodiments, the concentration of nickel in the barrier layer isbetween about 5% and 10% by weight, the concentration ofchromium—between about 25% and 30% by weight, the concentration oftitanium and aluminum—between about 30% and 35% by weight each. Thiscomposition of barrier layer 112 may be achieved by using one or moresputtering targets containing nickel, chromium, titanium, and aluminum,controlling concentration of these metals in the sputtering targets, andcontrolling power levels applied to each sputtering target. For example,two sputtering targets may be used. The first target may include nickeland chromium, while the second target may include titanium and aluminum.The weight ratio of nickel to chromium in the first target may be about4, while the weight ratio of titanium to aluminum in the second targetmay be about 1. These weight ratios may be achieved by usingcorresponding alloys for the entire target, target inserts made fromdifferent materials, or other features allowing combination of two ormore materials in the same target. The two targets may be exposed todifferent power levels. In the above example, the first target may beexposed to twice smaller power than the second target to achieve thedesired composition. The barrier can be deposited substantially free ofoxygen (e.g., predominantly as a metal) in the inert environment (e.g.,argon environment). Alternatively, some oxidant (e.g., 15% by volume ofO₂ in Ar) may be used to oxide the four metals. The concentration ofoxygen in the resulting barrier layer may be between about 0% and 5% byweight.

In some embodiments, nickel, chromium, titanium, and aluminum are alluniformly distributed throughout the barrier layer, i.e., its entirethickness and coverage area. Alternatively, the distribution ofcomponents may be non-uniform. For example, nickel and chromium may bemore concentrated along one interface than along another interface. Insome embodiments, a portion of the barrier layer near the interface withthe reflective layer includes more nickel for better adhesion to thereflective layer. In some embodiments, substantially no other componentsother than nickel, chromium, titanium, and aluminum are present inbarrier layer 112.

Barrier layer 112 may be amorphous metal. For purposes of thisdisclosure, an amorphous metal (also known metallic glass or glassymetal) is a solid metallic material, usually an alloy, which may haveless than 5% crystallinity by volume. For example, barrier layer 112 maybe a layer of a material, such as NiTiNb which may be configured to havea thickness between about 1.5 nm and 5 nm. In some examples, barrierlayer 112 has a thickness of 2.4 nm. Barrier layer 112 may be formedusing a deposition technique, such as sputtering. During the formingprocess, a small amount of oxygen may be mixed with Argon to create alayer of NiTiNb oxide having an oxygen content between 10% to 30% byatomic weight. In some embodiments, barrier layer 112 may have athickness of between about 1 Angstrom and 100 Angstroms or, morespecifically, between about 5 Angstroms and 30 Angstroms, and evenbetween about 10 Angstroms and 20 Angstroms.

Without being restricted to any particular theory, it is believed thatwhen the barrier layer is exposed to oxygen (e.g., during deposition ofthe top dielectric), some metals of the barrier layer (e.g., Cr, Ti, andAl) will be easily oxidized thereby consuming oxygen and preventingoxygen from penetrating through the barrier layer and reaching thereflective layer. As such, the barrier layer may be considered as ascavenging layer.

Top dielectric layer 114 may be similar to bottom dielectric layer 106described above. In some embodiments, top dielectric layer 114 may beconfigured to enhance coupling between top dielectric layer 114 andbarrier layer 112. Top dielectric layer 114 may include, at least inpart, tin oxide, zinc tin oxide, aluminum tin oxide, magnesium tinoxide, bismuth tin oxide, or niobium tin oxide. As previously discussed,barrier layer 112 may include a material, such as NiTiNb. In someembodiments, one or more materials included in top dielectric layer 114might not be entirely compatible with and might not connect or couplewell with nitrides, such as NiTiNb. Thus, according to some embodiments,top dielectric layer 114 may include, at least in part, a metal oxide,such as ZnO or ZnTiO. The inclusion of ZnO in top dielectric layer 114may increase the compatibility and coupling between top dielectric layer114 and barrier layer 112.

Top diffusion layer 116 may be similar to bottom diffusion layer 104described above. In some embodiments, top diffusion layer 116 (e.g.,formed from silicon nitride) may be more stoichiometric than bottomdiffusion layer 104 to give better mechanical durability and a smoothersurface. Bottom diffusion layer 104 (e.g., formed from silicon nitride)can be silicon-rich to make film denser for better diffusion effect.

Interface layer 115 may be a layer deposited between top dielectriclayer 114 and top diffusion layer 116. Interface layer 115 may beconfigured to prevent changes in the oxidation state of top dielectriclayer 114. Thus, interface layer 115 may prevent oxygen from migratingfrom or into top dielectric layer 114. For example, interface layer 115may prevent tin included in top dielectric layer 114 from transitioningfrom a +4 oxidation state to a +2 oxidation state. Preventing changes inthe oxidation state of top dielectric layer 114 preserves itstransmissivity. For example, a change in a substrate-side reflectance ofa partially fabricated panel that includes interface layer 115 and topdiffusion layer 116 may be less than 3% after a heat treatment process.In this way, interface layer 115 may protect one or more optical andchemical characteristics of top dielectric layer 114 during thesubsequent formation of other layers, such as top diffusion layer 116.Moreover, interface layer 115 may continue to protect top dielectriclayer 114 during subsequent manufacturing processes, such as heattreatment of article 100. Thus, interface layer 115 may be configured toprovide protection for top dielectric layer 114 in a way that iscompatible with multiple fabrication processes that may be used whenmanufacturing article 100.

In some embodiments, interface layer 115 may include one or morematerials that are highly transmissive and are high band gap materialsthat have strong oxygen bonds. For example, interface layer 115 may bemade of a material that has a bandgap of at least 3 eV. Interface layer115 is preferably highly transmissive to maintain a high transmissivityof article 100 which may be at least a portion of a panel of low-Eglass. Moreover, the materials included in interface layer 115preferably have oxygen bonds which are sufficiently strong to preventoxygen migration during a deposition of additional layers on top ofinterface layer 115, and during subsequent manufacturing processes, suchas heat treatment. Thus, the materials that form interface layer 115preferably have a transmissivity which is high enough to preserve theoptical performance of article 100, which may be low-E glass, and alsohave a presence of oxygen bonds strong enough to prevent the migrationof oxygen from a layer, such as top dielectric layer 114, duringdeposition of another layer which may utilize a highly reactiveenvironment, such as a nitrogen plasma environment, and during asubsequent manufacturing process, such as a heat treatment used totemper the low-E glass. In this way, interface layer 125 maysubstantially prevent nitrogen from the nitrogen plasma environment fromreaching top dielectric layer 114 and changing the oxidation state oftin in top dielectric layer 114.

As similarly discussed above, interface layer 115 may include one ormore materials that are highly transmissive and have a high band gap. Insome embodiments, interface layer 115 may include one or more metaloxides, such as zinc oxide, titanium oxide, and tantalum oxide. Forexample, top dielectric layer 114 may include Zn2SnOx and interfacelayer 115 may include ZnO. As previously discussed above, top dielectriclayer 114 may include a combination of Zn2SnOx and ZnO to increasecoupling between top dielectric layer 114 and barrier layer 112, whichmay include NiTiNb, as well as to maintain high transmissivity of topdielectric layer 114. Returning to the previous example, interface layer115 may be an additional layer of ZnO that is highly transmissive andisolates and protects top dielectric layer 114 from changes in oxidationstates.

In some embodiments, interface layer 115 has a thickness which isconfigured to provide a high transmissivity while also providing abarrier to migration of oxygen from top dielectric layer 114. Ifinterface layer 115 is too thin, interface layer 115 might not providesufficient isolation between top dielectric layer 114 and top diffusionlayer 116 to maintain the optical and chemical properties of topdielectric layer 114. For example, if interface layer 115 is too thin,it might not be able to prevent the migration of materials into and outof top dielectric layer 114. Moreover, if interface layer 115 is toothick, various undesirable results may occur. For example, interfacelayer 115 might not be sufficiently transmissive to meet specificationrequirements for the low-E panel. Moreover, if interface layer 115 istoo thick, undesirable results may occur as a result of subsequentprocessing and manufacturing steps, such as crystallization which mayoccur during a heat treatment. In such a case, the transmission andisolation characteristics of interface layer 115 may be degraded afterthe application of a heat treatment, and the transmissivity of article100 may be reduced.

Accordingly, interface layer 115 may be configured to have a thicknessthat maintains high transmissivity while also providingisolation/protection of top dielectric layer 114. Applicants havedetermined that interface layer 115 may be configured to have athickness between 2 nm and 8 nm. When configured to have such athickness, interface layer 115 is highly transmissive and provides goodisolation of top dielectric layer 114. Interface layer 115 may befurther configured to have a thickness between 3 nm and 5 nm. In oneexample, interface layer 115 has a thickness of 4 nm.

Interface layer 115 may also be configured to have a particular form orstructure that further provides isolation and/or protection of topdielectric layer 114. For example, interface layer 115 may include anamorphous material, such as amorphous ZnO. In some embodiments,interface layer 115 may be partially amorphous, and may be at leastabout 25% amorphous. In some embodiments, interface layer 115 may be atleast about 50% amorphous. Furthermore, interface layer 115 may beconfigured such that it is made of a material that is entirelyamorphous.

In some embodiments, reflective layer 110 included in stack 120 may havea sheet resistance of between about 6 Ohm/square to 8 Ohm/square for athickness of a silver reflective layer between 80 Angstroms and 90Angstroms. The sheet resistance may be between about 2 Ohm/square to 4Ohm/square for a thickness of a silver reflective layer between 100Angstroms and 140 Angstroms.

In some embodiments, a stack may include multiple reflective layers inorder to achieve a specific performance. For example, the stack mayinclude two, three, or more reflective layers. The multiple reflectivelayers may have the same or different composition and/or thicknesses.Each new reflective layer may have a corresponding dielectric layer(e.g., at least one layer formed in between two reflective layers), aseed layer, and a barrier layer. FIG. 1 illustrates a portion 118 ofstack 120 that may be repeated. Stack portion includes dielectric layer106 (or dielectric layer 114), seed layer 108, reflective layer 110, andbarrier layer 112. In some embodiments, portion 118 may not include seedlayer 108.

FIG. 2 is a schematic illustration of another article 200 including asubstrate 201 and a stack including two reflective layers 206 and 216,in accordance with some embodiments. Each one of reflective layers 206and 216 is a part of a separate stack portion that includes otherlayers, i.e., reflective layer 206 is a part of first stack portion 210,while reflective layer 216 is a part of second stack portion 220. Otherlayers in first stack portion 210 include dielectric layer 204, seedlayer 205, and barrier layer 207. Likewise, in addition to reflectivelayer 216, second stack portion 220 includes dielectric layer 214, seedlayer 215, and barrier layer 217. It should be noted that reflectivelayers 206 and 216 are separated by only one dielectric layer 214. Theoverall article 200 also includes bottom diffusion layer 202, topdielectric layer 224, and top diffusion layer 226. Article 200 mayfurther include interface layer 225. As similarly discussed above withreference to FIG. 1, a reflective layer, such as reflective layer 216,may include silver. Moreover, a dielectric layer may include TiO₂, ZnO,SnO₂, SiAlN, or ZnSn. Furthermore, a barrier layer may include an alloythat includes one or more of nickel, chromium, titanium, and aluminum.In some embodiments, a seed layer may include a metal oxide, such aszinc oxide. Moreover, a diffusion layer may include silicon nitride. Aninterface layer, such as interface layer 225, may include at least oneof zinc oxide, titanium oxide, and tantalum oxide.

FIG. 3 is a schematic illustration of yet another article 300 includinga substrate 301 and three reflective layers, each being a part of asseparate stack portion. Specifically, article 300 includes first stackportion 310 having reflective layer 312, second stack portion 320 havingreflective layer 322, and third stack portion 330 having reflectivelayer 332. Other layers of article 300 also bottom diffusion layer 302,top dielectric layer 334, and top diffusion layer 336. Article 300 mayfurther include interface layer 335. As similarly discussed above withreference to FIG. 1 and FIG. 2, a reflective layer, such as reflectivelayer 322, may include silver. Moreover, a dielectric layer may includeTiO₂, ZnO, SnO₂, SiAlN, or ZnSn. Furthermore, a barrier layer mayinclude an alloy that includes one or more of nickel, chromium,titanium, and aluminum. In some embodiments, a seed layer may include ametal oxide, such as zinc oxide. Moreover, a diffusion layer may includesilicon nitride. An interface layer, such as interface layer 335, mayinclude at least one of zinc oxide, titanium oxide, and tantalum oxide.

Processing Examples

FIG. 4 is a process flowchart corresponding to a method 400 of formingan article including a silver reflective layer and a barrier layer forprotecting this reflective layer from oxidation, in accordance with someembodiments. Method 400 may commence with providing a substrate duringoperation 402. In some embodiments, the provided substrate is a glasssubstrate. The substrate may include one or more previous depositedlayers. For example, the substrate may include a bottom diffusion layer,a bottom dielectric layer, and a seed layer. In some embodiments, one ofmore of these layers may not be present on the substrate. Variousexamples of these layers and substrates are described above withreference to FIG. 1.

Method 400 may proceed with forming a reflective layer over thesubstrate during operation 404 or, more specifically, over one or morelayers previously formed on the provided substrate. This operation mayinvolve sputtering silver in a non-reactive environment. The silverlayer may be deposited in an argon environment at a pressure of 2millitorr using 90 W power applied over a sputter area of about 12 cm²resulting in a power density of about 7500 W/m². The resultingdeposition rate was about 2.9 Angstroms per second. The target tosubstrate spacing was about 240 millimeters. The thickness of thereflective layer may be between about 50 Angstroms and 200 Angstroms. Insome embodiments, the same reflective layer is provided in all siteisolated regions of the substrate. In other words, the reflective layerhas the same composition and thickness in all site isolated regions ofthe substrate. This uniformity may be used to provide control and vary,for example, parameters of another layer.

Method 400 may proceed with forming a barrier layer over the reflectivelayer during operation 406. As noted above, the reflective layer may beformed from a quaternary alloy including nickel, chromium, titanium, andaluminum that is formed by co-sputtering of these four metals in anon-reactive environment. In some embodiments, the barrier layer isdeposited in the same processing chamber as the reflective layer withoutbreaking the vacuum in the chamber. Overall, the reflective layer needsto be protected from oxygen prior to deposition of the barrier layer. Insome embodiments, a partially fabricated article may be maintained in anoxygen-free environment after forming the reflective layer and prior toforming the barrier layer.

Operation 406 may use a single sputtering target that includes all fourmetals. Alternatively, multiple targets, each including one or moremetals, may be used. When a target includes multiple metals, thesemetals may be in a form of an alloy arranged into a unified body or maybe present as separate components of the target. The composition ofmetals in the one or more targets may correspond to the desiredcomposition of the barrier layer. For example, a target including 5-10%by weight of nickel, 25-30% by weight of chromium, 30-35% by weight oftitanium, and 30-35% by weight of aluminum may be used. In someembodiments, one target may include nickel and chromium (e.g., having a4:1 weight ratio of nickel to chromium) and another target may includetitanium and aluminum (e.g., having a 1:1 weight ratio). The power levelused on the titanium-aluminum target may double of that used for thenickel-chromium level, e.g., 200 W and 100 W respectively for 3-inchtargets positioned about 12 inches away from the substrate resulting ina 2-4 Angstroms per minute deposition rate.

Method 400 may then proceed with forming a dielectric layer over thebarrier layer during operation 408. This operation may involvesputtering titanium or tin in an oxygen containing environment. Duringthis operation, the barrier layer prevents oxygen in the oxygencontaining environment from reaching and reacting with metallic silverin the reflective layer.

At operation 409, an interface layer may be formed. As similarlydiscussed above, the interface layer may be made of a material that ishighly transmissive and has a high band gap. For example, the interfacelayer may be made of a material, such as zinc oxide, titanium oxide, ortantalum oxide. The interface layer may be formed by a depositiontechnique, such as sputtering. The interface layer may be depositeduntil a particular thickness is achieved, such as between 2 nm and 8 nm.

As similarly discussed above, according to various embodiments, the sametype of interface layer, and the same process for forming the interfacelayer may be used regardless of which type of fabrication process isused to form the article which may be a portion or part of a low-Epanel. For example, the same deposition technique and the same interfacelayer may be used regardless of whether the low-E panel is fabricated inaccordance with an as-coated process, or whether the low-E panel isfabricated in accordance with a heat treatment process.

If another reflective layer needs to be deposited on the substrate,operations 404-408 may be repeated as indicated by decision block 410.

CONCLUSION

Although the foregoing concepts have been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. It should be noted that there are many alternative waysof implementing the processes, systems, and apparatuses. Accordingly,the present embodiments are to be considered as illustrative and notrestrictive.

What is claimed is:
 1. A method for forming a low emissivity panel, themethod comprising: providing a partially fabricated panel, the partiallyfabricated panel comprising a substrate, a reflective layer formed overthe substrate, and a top dielectric layer formed over the reflectivelayer such that the reflective layer is formed between the substrate andthe top dielectric layer, and wherein the top dielectric layer comprisestin having an oxidation state of +4; forming an interface layer over thetop dielectric layer; and forming a top diffusion layer over theinterface layer, wherein the top diffusion layer is formed in a nitrogenplasma environment, wherein the interface layer has a band gap of atleast 3.0 eV, and wherein a material of the interface layer is at leastabout 25% amorphous.
 2. The method of claim 1, wherein the interfacelayer directly interfaces the top diffusion layer and the top dielectriclayer.
 3. The method of claim 1, wherein the top dielectric layercomprises one of tin oxide, zinc tin oxide, aluminum tin oxide,magnesium tin oxide, bismuth tin oxide, or niobium tin oxide.
 4. Themethod of claim 1, wherein a material of the interface layer is at leastabout 50% amorphous.
 5. The method of claim 1, wherein a material of theinterface layer is less than 5% crystalline by volume.
 6. The method ofclaim 1, wherein the interface layer comprises zinc oxide.
 7. The methodof claim 1, wherein the interface layer comprises titanium oxide.
 8. Themethod of claim 1, wherein the interface layer comprises tantalum oxide.9. The method of claim 1, wherein the interface layer has a thickness ofbetween about 2 nanometers and 8 nanometers.
 10. The method of claim 1,wherein the top diffusion layer comprises silicon nitride.
 11. Themethod of claim 1, wherein the top diffusion layer is formed usingsputtering of a silicon target in the nitrogen plasma environment. 12.The method of claim 1, wherein the partially fabricated panel furthercomprises a barrier layer disposed between the reflective layer and thetop dielectric layer, the barrier layer comprising nickel, titanium, andniobium.
 13. The method of claim 12, wherein the partially fabricatedpanel further comprises a bottom diffusion layer deposited between thesubstrate and the reflective layer, a bottom dielectric layer depositedbetween the bottom diffusion layer and the substrate, and a seed layerformed between the bottom dielectric layer and the reflective layer. 14.The method of claim 1, further comprising, after forming the topdiffusion layer, heat treating the partially fabricated panel comprisingthe interface layer and the top diffusion layer.
 15. The method of claim14, wherein a change in a substrate-side reflectance of the partiallyfabricated panel comprising the interface layer and the top diffusionlayer is less than 3% after heat treating.
 16. The method of claim 1,wherein the interface layer is formed using reactive sputtering.
 17. Themethod of claim 1, wherein the top diffusion layer comprises siliconnitride, wherein the interface layer comprises zinc oxide, and whereinthe top dielectric layer comprises zinc tin oxide.
 18. The method ofclaim 1, wherein substantially all tin in the top dielectric layer hasthe oxidation state of +4.
 19. A method for forming a low emissivitypanel, the method comprising: providing a partially fabricated panel,the partially fabricated panel comprising a glass substrate, areflective layer formed over the glass substrate, and a top dielectriclayer formed over the reflective layer such that the reflective layer isformed between the substrate and the top dielectric layer, wherein thetop dielectric layer comprises zinc tin oxide; forming an interfacelayer over the top dielectric layer, wherein the interface layercomprises zinc oxide and has a thickness of between about 2 nm and 8 nm,and wherein the interface layer has a band gap of at least 3.0 eV; andforming a top diffusion layer over the interface layer, wherein the topdiffusion layer comprises silicon nitride and is formed using reactivesputtering in a nitrogen plasma environment, and wherein a material ofthe interface layer is at least about 50% amorphous.
 20. A lowemissivity panel comprising: a substrate; a reflective layer formed overthe substrate; a top dielectric layer formed over the reflective layersuch that the reflective layer is formed between the substrate and thetop dielectric layer, wherein the top dielectric layer comprises tinhaving an oxidation state of +4; an interface layer formed over the topdielectric layer such that the top dielectric layer is formed betweenthe reflective layer and the interface layer, wherein the interfacelayer comprises one of zinc oxide, titanium oxide, or tantalum oxide,wherein the interface layer has a band gap of at least 3.0 eV, andwherein a material of the interface layer is at least about 50%amorphous; and a top diffusion layer formed over the interface layersuch that the interface layer is formed between the top dielectric layerand the interface layer, wherein the top diffusion layer comprisessilicon nitride.